sanguin Posted June 19, 2018 Share Posted June 19, 2018 This may resemble the old discussion about Mustang hydraulics, but I seek some help. I want to build an F-86 Sabre, probably civilian, on the ground. Can anybody give me advice on the normal 'aircraft parked' position of the undercarriage doors? Lots of pictures do not clarify the situation... The main wheel doors are often hidden behind tanks but seem to be hanging vertically almost on the centreline with the smaller doors attached to or very close to the main legs, However the main nose wheel door has the dimensions of a barn door. I have seen one comment that it retracted as soon as the nose wheel was lowered as it destabilised the aircraft in yaw on the approach. If this is true then I assume it then bled down, like the airbrakes, when parked. So is a parked F-86 usually seen with it all hanging down as the hydraulic pressure falls or are at least some of the doors manually locked in the up position? All advice gratefully received, John Link to comment Share on other sites More sharing options...
bentwaters81tfw Posted June 19, 2018 Share Posted June 19, 2018 As the pressure drops, it all hangs out. Gear doors, speed brakes and slats. Link to comment Share on other sites More sharing options...
sanguin Posted June 19, 2018 Author Share Posted June 19, 2018 My thanks for such a clear and prompt response. All a'dangle it will be. John Link to comment Share on other sites More sharing options...
Julien Posted June 19, 2018 Share Posted June 19, 2018 F-86 slats work on air pressure, below a certain speed they come out. They can be pushed closed on the ground. Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 19, 2018 Share Posted June 19, 2018 (edited) Sabre gear doors are up when taxiing, when parked there is a switch that is activated by the ground crew, which opens the nose door and the two main doors. There is NO hydraulic pressure bleeding down. Before engine start, the switch is thrown, so that the doors will close as hyd pressure is gained. There are pics of them parked with gear doors up, and pics of them with open doors. Pick your choose. Edit: the switch is in the LH gear well Tony Edited June 20, 2018 by Tony Edmundson 3 1 Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 19, 2018 Share Posted June 19, 2018 2 hours ago, bentwaters81tfw said: As the pressure drops, it all hangs out. Gear doors, speed brakes and slats. Negative, a big negative ! Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 20, 2018 Share Posted June 20, 2018 Sanguin, be wary of the ‘duff gen’ given off around here. Cheers, Tony Link to comment Share on other sites More sharing options...
bentwaters81tfw Posted June 20, 2018 Share Posted June 20, 2018 Please do enlighten us then, Tony. I am aware the slats are operated by air 'pressure', but they stay extended unless pushed back by hand. Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 20, 2018 Share Posted June 20, 2018 3 hours ago, bentwaters81tfw said: Please do enlighten us then, Tony. I am aware the slats are operated by air 'pressure', but they stay extended unless pushed back by hand. I did,concerning the gear doors,(the OPs original question) also the speedbrakes are selected out or in at shutdown and do not bleed. Tony Link to comment Share on other sites More sharing options...
sanguin Posted June 20, 2018 Author Share Posted June 20, 2018 Gentlemen, my thanks to you both for responding and special thanks to Tony for sharing his technical knowledge with us. Over many years of browsing and using this site I am still in awe of the knowledge of others. The incidence of 'duff gen' is is rare and always given with the best of intentions; those that know the facts will then usually correct it and we all learn. One of the many joys of Britmodeller. My request was because having looked at many pictures of Sabres on the ground there seemed to be no concensus, particularly with the large nose wheel door. Clear images of the central main wheel doors are commonly less visible but the few I have seen also had either 'up' or 'down'. I must admit that most pictures seem to show the air brakes extended, but not all. It was this mixture of positions that provoked my question. As to the slats, I must confess that to be honest I never really noticed which must be a sign of old age and being unable to cope with both wheels and wings at the same time! So the main doors are either open or closed together, the airbrakes can be open or closed without any reference to the undercarriage doors and the slats may be left open or pushed closed by the ground crew. Hydraulic bleed down is not a relevant factor but it is the attention of the pilot and ground crew that makes the decision. That makes the build a bit easier for me, then. Anything for a tidy aeroplane and fewer fiddly bits to paint. John 1 Link to comment Share on other sites More sharing options...
Terry1954 Posted June 20, 2018 Share Posted June 20, 2018 Hi @sanguin I will add that as I am becoming acutely aware, building sabres is much fun. I'm on my third in a year, with six more in the stash! And those doors look so cool when they droop down like that: You will get some good help on here especially from @Tony Edmundson and @Sabrejet and many others I have not mentioned. Terry Link to comment Share on other sites More sharing options...
bentwaters81tfw Posted June 20, 2018 Share Posted June 20, 2018 48 minutes ago, Tony Edmundson said: I did,concerning the gear doors,(the OPs original question) also the speedbrakes are selected out or in at shutdown and do not bleed. Tony Sorry, I had not gone that far back on the thread. I have learned something today, thank you. I watched a video on you tube showing a Sabre start up and taxi. Classic example of closing the doors and brakes. 5 Link to comment Share on other sites More sharing options...
sanguin Posted June 20, 2018 Author Share Posted June 20, 2018 Brilliant! The link to that video should be on a sticker on every F-86 kit. That would prevent the elderly from spending hours of indecision looking at still pictures and failing to decide what the hell was going on. Thanks again, John Link to comment Share on other sites More sharing options...
Seawinder Posted June 20, 2018 Share Posted June 20, 2018 FWIW, I was told by an F-86 ex-pilot that the airbrakes were left open more often than not when the plane was parked. I can't remember why this was done, but I think it was to give access for some sort of inspection. Link to comment Share on other sites More sharing options...
Corsairfoxfouruncle Posted June 20, 2018 Share Posted June 20, 2018 (edited) 4 hours ago, Seawinder said: I think it was to give access for some sort of inspection. I agree however as someone who went through training for Aircraft Airframe & Powerplant mechanics. I would add it also causes less stress on the high pressure system if its just hanging free. If its stowed and under pressure it probably isn't good for hoses and fittings long term. Edited June 20, 2018 by Corsairfoxfouruncle Link to comment Share on other sites More sharing options...
Sabrejet Posted June 20, 2018 Share Posted June 20, 2018 There is an accumulator pressure gauge in the stbd/RH speed brake well (F-86E/F): hence the need to leave them open for pre-flight. SJ 2 Link to comment Share on other sites More sharing options...
Sabrejet Posted June 20, 2018 Share Posted June 20, 2018 And here... 4 3 Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 20, 2018 Share Posted June 20, 2018 In that above graphic, see under Left Wing & Leading Edge, the pilot is to ensure the Gear Door switch is in the correct position. Tony 1 Link to comment Share on other sites More sharing options...
Tony Edmundson Posted June 20, 2018 Share Posted June 20, 2018 4 hours ago, Corsairfoxfouruncle said: I agree however as someone who went through training for Aircraft Airframe & Powerplant mechanics. I would add it also causes less stress on the high pressure system if its just hanging free. If its stowed and under pressure it probably isn't good for hoses and fittings long term. When the airbrakes are closed, they lock and the switch is set to neutral, so there isn’t any pressure along lines that are close to the exhaust pipe. There is a neutral setting on the air brake switch. Cheers, Tony 2 Link to comment Share on other sites More sharing options...
sanguin Posted June 21, 2018 Author Share Posted June 21, 2018 Thanks again to you all for enlightening us. Now we all know it's only after the ground crew have done all of their preflight checks that our fighter pilot hero is allowed to swagger out to 'kick the tyres (tires) and light the fires'... So a bit of detail in the air brake recesses is now called for. but that is a fair swap for covering the wheel wells. John 1 1 Link to comment Share on other sites More sharing options...
Winnie Posted June 25, 2018 Share Posted June 25, 2018 On 6/19/2018 at 4:27 PM, bentwaters81tfw said: As the pressure drops, it all hangs out. Gear doors, speed brakes and slats. Slats I believe are non-hydraulic and purely come out by gravity/slow speed. Link to comment Share on other sites More sharing options...
Paul J Posted June 25, 2018 Share Posted June 25, 2018 A small tip when modeling F-86 speed brakes open and sagging,,,, cut the lower of the 'hinge tabs' shorter but not too much and leave the top ones as is. This way you will get a suitable sagged open brake supported by the actuator. 1 Link to comment Share on other sites More sharing options...
RODH2 Posted June 25, 2018 Share Posted June 25, 2018 Not to be pedantic, (so I will be), they don't "sag", they just open that way. (The air brakes, that is!).🙂 1 Link to comment Share on other sites More sharing options...
Terry1954 Posted June 25, 2018 Share Posted June 25, 2018 20 minutes ago, Paul J said: A small tip when modeling F-86 speed brakes open and sagging,,,, cut the lower of the 'hinge tabs' shorter but not too much and leave the top ones as is. This way you will get a suitable sagged open brake supported by the actuator. Good tip, I see what you mean. I'm contemplating open airbrakes on my current Airfix buiild (also WIP here) but trying to work out the internals at the moment. The Airfix ones look a bit basic and also appear to be replicated both sides, whereas I have pictures that show differences from one side to the other. Thinking time ..... 🤔 Terry Link to comment Share on other sites More sharing options...
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